Imidazolidine carboxylic acids and esters as blood platelet aggregation inhibitors

ABSTRACT

Heterocyclic acids and esters useful as inhibitors of mammalian blood platelet aggregation characterized by Formula I are disclosed. 
     
         HET.sub.1 -(CH.sub.2).sub.n CO.sub.2 R                     (I) 
    
     Formula I compounds are those wherein n is 6-9, R is hydrogen, lower alkyl or an alkali metal ion, and HET 1  is the heterocyclic radical 2,5-dioxo-3,4-diphenylimidazolidin-1-yl.

BACKGROUND OF THE INVENTION

This invention generally pertains to heterocyclic carbon compoundshaving drug and bio-affecting properties and to their preparation anduse. in particular, the invention is concerned with various heterocyclicderivatives characterized by Formula I, infra., which are inhibitors ofblood platelet aggregation.

United States patents relating to the carboxylic acid and esterderivatives of the various heterocycles disclosed herein are as follows:

Imidazolidine compounds in Field of Search 514/398 and 5481308, 312,314.

van der Burg, U.S. Pat. No. 3,965,114 discloses imidazolidinederivatives having anticholinergic and anticonvulsant properties offormula (1). ##STR1## Whootton, et al., U.S. Pat. No. 4,237,131discloses hydantoins having bronchodilator activity of formula (2).##STR2## Lautenschlager, et al., U.S. Pat. No. 4,330,550 disclosesomega-(2-oxo-4-imidazoline-1-yl) alkanoic acids and esters havingantithrombogenic and analgesic activity of formula (3). ##STR3## Mai, etal., U.S. Pat. No. 4,709,042 discloses a process for preparing2-(1-hydroxyalkyl)-5,5-diphenyl hydantoin of the formual (4). ##STR4##Matsuno, et al., U.S. Pat. No. 4,797,493 discloses imidazolines havingultraviolet-absorbing properties of formula (5). ##STR5##

SUMMARY OF THE INVENTION

In its broadest aspect, this invention is concerned with heterocycliccarboxylic acids and esters of Formula I

    HET.sub.1 -(CH.sub.2).sub.n CO.sub.2 R                     (I)

wherein HET₁, R, R₁, and n are defined below which are inhibitors ofadenosine diphosphate and collagen-induced aggregation of humanplatelet-rich plasma and are particularly useful as inhibitors ofmammalian blood platelet aggregation.

Another embodiment of the invention relates to the alkali metal salts ofcarboxylic acids of Formula I (R is hydrogen). A further embodimentconcerns pharmaceutical compositions comprised of a Formula I compoundcombined with at least one pharmaceutically acceptable excipient. Yetanother embodiment relates to a method for inhibiting blood plateletaggregation in a mammal which comprises administering a therapeuticallyeffective amount of a compound of Fcrmula I or an alkali metal saltthereof where R is hydrogen to a mammal in need of such treatment.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to inhibitors of mammalian blood plateletaggregation of Formula I

    HET.sub.1 -(CH.sub.2).sub.n CO.sub.2 R                     (I)

wherein n is 6-9, R is hydrogen, lower alkyl or an alkali metal ion, andHET₁ is the heterocyclic radical ##STR6##2,5-dioxo-3,4-diphenylimidazolidin-1-yl.

It is understood that as used herein limitations of Formula I aredefined as follows.

The term "lower alkyl" refers to a branched or unbranched saturatedhydrocarbon chain containing from 1-4 carbon atoms; specifically,methyl, ethyl, n-propyl, isopropyl, n-butyl, secondary butyl, andtertiary butyl.

The term "lower alkanol" denotes an alcohol having 1-4 carbon atomsdefined by "lower alkyl".

The symbol "Ph" represents phenyl.

The term "alkali metal ion" refers to ions derived from the alkalimetals, most preferably sodium and potassium.

According to the present invention the compounds characterized byFormula I are obtained by a process comprising:

(a) hydrolyzing a compound of Formula (I^(a))

    HET.sub.1 -(CH.sub.2).sub.n CO.sub.2 R.sup.a               (I.sup.a)

wherein HET₁ is as defined above, n is 6-9 and R^(a) is lower alkyl, or

(b) esterifying a compound of Formula (I^(b))

    HET.sub.1 -(CH.sub.2).sub.n CO.sub.2 H                     (I.sup.b)

wherein HET₁ is as defined above and n is 6-9 with a lower alkanol, or

(c) alkylating HET₁ -H wherein HET¹ is as defined above with a compoundof Formula (III)

    X-(CH.sub.2).sub.n CO.sub.2 R.sup.a                        (III)

wherein X is halogen, preferably bromine,, n is 6 to 9, and R^(a) islower alkyl.

Scheme 1 below illustrates the foregoing process. ##STR7##

Compounds of Formula I are conventionally prepared as shown in Scheme 1by base-mediated alkylation of the parent heterocycle (III) with a loweralkanol ester of an omega-halogenalkanoic acid (IV) to provide esters(I^(a)). Alkylation can be carried out with sodium hydride, potassiumhydride, potassium t-butoxide in suitable solvents such astetrahydrofuran and dimethylformamide with conditions dependent upon theidentity of the heterocycle and the acidity of the proton beingreplaced. Preferred alkylating conditions empoly sodium hydride indimethylformamide (DMF) at room temerpature or potassium carbonate inDMF at 110° C. In those instances where the alkylation results inmixtures of regioisomers, separation is readily accomplished bychromatography on silica gel. Structural assignments are made fromconsideration of the ¹ H and ¹³ C NMR spectra. The heterocycles (III)employed as starting material are synthesized by methods reported in thechemical literature or by minor modifications thereof readily apparentto a skilled chemist.

Esters (I^(a)) are converted to the corresponding acids (I^(b)) underthe influence of either aqueous alkali or aqueous acid depending uponthe sensitivity of the heterocycle. Conversely, acids (I^(b)) areconventionally converted to the corresponding esters (I^(a)) by heatingthe acid in a lower alkanol in the presence of an inorganic acid such ashydrochloric, sulfuric and the like.

Alkali metal salts of Formula I carboxylic acids (R is an alkali metalion) are conventionally prepared by dissolving the acid in a suitablesolvent such as methanol, adding a molar equivalent of an alkali basesuch as sodium methoxide, and precipitating the salt or removing thesolvent.

As stated above, the compounds of Formula I have pharmacologicalproperties which make them particularly useful as inhibitors of bloodplatelet aggregation.

Platelet aggregation is considered part of a complex physiologicalmechanism for formation of a thrombus in the vascular system.Thromboembolic phenomena, i.e., the formation of thrombi, are involvedin hemostasis and a number of disease states in mammals includingthrombophlebitis, phlebothrombosis, cerebral thrombosis, coronarythrombosis and retinal vessel thrombosis. An increase in propensity forplatelet aggregation, sometimes referred to as platelet adhesiveness, isobserved following parturition, surgical operations such as coronaryartery bypass surgery, organ transplant, angioplasty, prosthetic heartvalve implants to name a few and in ischaemic heart disease,artherosclerosis, multiple sclerosis, intracranial tumors,thromboembolism, and hyperlipemia: refer to A. Poplawski, et al., J.Artherosclerosis Research, 8, 721 (1968). Thus, the compounds of theinvention which have antithrombogenic actions (inhibit blood plateletaggregation) are useful in prevention or treatment of conditionsinvolving platelet aggregation and thrombosis such as the above. Theinstant compounds are also considered to have antimetastatic potentialin view of their platelet inhibition properties.

The pharmacological properties of the instant compounds can bedemonstrated by conventional in vitro and in vivo biological tests suchas the following.

IN VITRO INHIBITION OF HUMAN PLATELET AGGREGATION

The aggregometer method of Born, C. V. R., J. Physiol., (London), 1962,162, 67-68, as modified by Mustard, J. F., et al., J. Lab. Clin. Med.1964, 64, 548-599 was used to assess the in vitro activity of thevarious compounds as to the inhibition of adenosine diphosphate (ADP)and collagen-induced platelet aggregation. The human volunteer donor'sarm is cleansed with 70% ethyl alcohol. A sterile 20 ml syringe andneedle are used to withdraw 20 ml of blood. The blood is immediatelyadded to a test tube containing 3.8% sodium citrate to prevent clotting(1 part citrate to 9 parts blood).

Platelet rich plasma (PRP) was separated by centrifugation for 10minutes at 1000 rpm (140 xg) from citrated (3.8%) human blood. Allglassware used for preparation of PRP is silicon treated. ADP in finalconcentration of 0.5 mcg/mL or 0.05 mL of a collagen suspension preparedaccording to the method described by Evans, G., et al., J. Exp. Med.,1968, 128, 877-894 was used to induce aggregation. The various compoundstested were dissolved in dimethylsulfoxide (DMSO) so that 5 mcl added tothe platelet rich plasma would yield the desired test concentration.Vehicle control trials were done and compared with aggregation inducedin platelet rich plasma containing various concentrations of the testcompounds. Dose response curves were obtained and InhibitorConcentration (IC₅₀) values calculated. In this test, the IC₅₀ valuesfor dipyridamole, a clinically useful antithrombogenic agent, are 512mcg/ml vs. ADP and 245 mcg/ml vs collagen. Results for 50% inhibition ofADP-induced aggregation are given hereinafter.

                  TABLE 1                                                         ______________________________________                                        Inhibition of Human Platelet Aggregation                                      of Formula I Compounds (IC.sub.50 mcg/ml)                                     HET.sub.1 -(CH.sub.2).sub.n CO.sub.2 R                                                                             vs. ADP                                  Example  HET.sub.1      n       R    mcg/ml                                   ______________________________________                                        1        2,5-dioxo-3,4-diphenyl-                                                                      8       CH.sub.3                                                                           32                                                imidazolidin-1-yl                                                    2        2,5-dioxo-3,4-diphenyl-                                                                      8       H    11.9                                              imidazolidin-1-yl                                                    ______________________________________                                    

The acids are particularly potent inhibitors of ADP-induced aggregationof human platelets. While the esters are generally less active than theparent acid, they are useful as pro-drugs in vivo where they arehydrolyzed to the corresponding acid.

The dosage employed in the therapeutic methods of the instant inventionwill vary with the form of administration, the particular compoundchosen, the subject being tested and the effect desired. Suitableeffective doses in animals range from 0.1-50 mg/kg body weight orallyand from 0.05-10 mg/kg body weight parenterally (generally characterizedas subcutaneous, intramuscular, and intravenous injection). It iscontemplated that the effective unit dose in man will range from 1 to100 mg and preferably from 1 to 20 mg administered one to three times aday. In accordance with conventional clinical practice, the effectivedose can be determined by administering a Formula I compound at a dosagesubstantially less than the dose of the compound which is thought to beeffective and then increasing the dosage in small increments until thedesired effect is achieved.

In carrying out the instant therapeutic methods, the active ingredientof Formula I or alkali metal salts of Formula I carboxylic acids arepreferably administered with a pharmaceutically acceptable carrier andsuch compositions constitute part of the instant invention. Suitabledosage forms for oral use are tablets, dispersible powders, granules,capsules, syrups and elixirs. Examples of parenteral forms aresolutions, suspension, dispersions, emulsions, and the like. Thecompositions for oral use may contain one or more conventionaladjuvants, such as sweetening agents, flavoring agents, coloring agentsand preserving agents, in order to provide a composition of suitablepharmaceutical elegance. Tablets may contain the active ingredient inadmixture with conventional pharmaceutical acceptable excipientsincluding inert diluents such as calcium carbonate, sodium carbonate,lactose and talc: granulating and disintegrating agents such as starchand alginic acid: binding agents such as starch, gelatin and acacia andlubricating agents such as magnesium stearate, stearic acid and talc.The tablets may be uncoated or coated by known techniques to delaydisintegration and absorption in the gastrointestinal tract and therebyprovide a sustained action over a longer period. Similarly, suspension,syrups and elixirs may contain the active ingredient in admixture withany of the conventional excipients utilized for the preparation of suchcompositions such as suspending agents (e.g., methylcellulose,tragacanth, and sodium alginate), wetting agents (e.g., lecithin,polyoxyethylene stearate) and preservatives such asethyl-p-hydroxybenzoate. Capsules may contain the active ingredientalone or admixed with an inert solid diluent such as calcium carbonate,calcium phosphate and kaolin. The injectible compositions are formulatedas known in the art and may contain appropriate dispersing or wettingagents and suspending agents identical or similar to those mentionedabove.

The following examples are given by way of illustration and are not tobe construed as limiting the invention in any way inasmuch as manyvariations of the invention are possible within the spirit of theinvention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

In the following examples, all temperatures are given in degreesCentigrade. Melting points were recorded on a Thomas-Hoover capillarmelting point apparatus and are uncorrected. Proton magnetic resonance(¹ H-NMR) spectra were recorded on a Bruker AM 300, Bruker WM 360 orVarian Gemini 300 spectrometer. All spectra were determined in CDCl₃ orDMSO-d₆ unless otherwise indicated and chemical shifts are reported indelta units downfield from the internal standard tetramethylsilane (TMS)and interproton coupling constants are reported in Hertz (Hz). Splittingpatterns are designated as follows: s, singlet: d, doublet: t, triplet:q, quartet: m, multiplet: br, broad peak: and dd, doublet of doublet.

EXAMPLE 1 ##STR8##

Diethyl axodicarboxylate (1.39 g, 8 mmol) in THF (5 mL, was addeddropwise to a stirred solution of methyl 9-hydroxynonanoate (1.50 g, 8mmol), 3,4-diphenylimidazolidine-2,5-dione (2.02 g, 8 mmol) obtainedaccording to the procedure of K. C. Joshi, et al., J. Het. Chem., 18,1651-1653 (1981) and triphenylphosphine (2.10 g, 8 mmol) in THF (35 mL).The mixture was stirred at room temperature for 72 hours, the THFremoved in vacuo and the residue triturated with a mixture of hexanesand diethyl ether. The mixture was filtered, the filtrate concentratedand subjected to chromatography on a column of silica gel using amixture of hexanes and ethyl acetate (3:2) as eluent. Elution gavemethyl 2,5-dioxo-3,4-diphenyl-1-imidazolidinenonanoate (2.78 g, 82%), mp69°-72° C.

Anal. Calcd. for C₂₅ H₃₀ N₂ O₄ : C, 71.07: H, 7.16: N, 6.65. Found: C,71.13: H, 7.19: N, 6.66%.

¹ H-NMR (CDCl₃) delta: 1.20 to 1.40 (8H, m), 1.50 to 1.70 (4H, m), 2.25(2H, t, J=6Hz), 3.55 (2H, t, J=6Hz), 3.61 (3H, s), 5.41 (1H, s), 7.03(1H, t, J=6.5Hz), 7.10 to 7.40 (7H, m) and 7.45 (2H, d, J=6.5Hz).

EXAMPLE 2 ##STR9##

A mixture of methyl 2,5-dioxo-3,4-diphenyl-1-imidazolidinenonanoate(3.00 g, 7 mmol) and 6N HCl solution (30 mL) was heated at reflux for 22hours. The mixture was cooled, extracted with CH₂ Cl₂ and the combinedextracts washed with water and twice with saturated sodium chloridesolution. After drying over sodium sulfate, the solvent was evaporatedand the residue chromatographed on a column of silica gel using amixture of hexanes and ethyl acetate (2:1) as eluent. Elution gave2,5-dioxo-3,4-diphenyl-1-imidazolidinenonanoic acid (1.06 g, 36%) afterrecrystallization from a mixture of hexanes, diethyl ether and CH₂ Cl₂(6:2:2), mp 111.5°-112.5° C. Anal. Calcd. for C₂₄ H₂₈ N₂ O₄ : C, 70.57:H, 6.91: N, 6.86. Found: C, 70.45: H, 7.05: N, 6.75%.

¹ H-NMR (CDCl₃) delta: 1.20 to 1.40 (6H, m), 1.50 to 1.80 (4H, m), 2.14(2H, t, J=6Hz), 3.61 (2H, t, J=6Hz), 5.42 (1H, s), 7.09 (1H, t, J=6Hz)and 7.15 to 7.60 (9H, m).

What is claimed is:
 1. A compound of Formula I

    HET.sub.1 -(CH.sub.2).sub.n CO.sub.2 R                     (I)

wherein n is 6 to 9; R is hydrogen or lower alkyl or an alkali metalion; and HET₁ is the heterocyclic radical ##STR10## 2.5-dioxo-3,4-diphenylimidazolidin-1-yl.
 2. The compound of claim 1 whichis methyl 2,5-dioxo-3,4-diphenyl-1-imidazolidinenonanoate.
 3. Thecompound of claim 1 which is2,5-dioxo-3,4-diphenyl-1-imidazolidinenonanoic acid.
 4. The method forinhibiting blood platelet aggregation in a mammal which comprisesadministering a therapeutically effective amount of a compound ofclaim
 1. 5. The pharmaceutical composition for inhibiting blood plateletaggregation comprising a therapeutically effective amount of a compoundof claim 1 and a pharmaceutical carrier.